Java and Its JVM Relatives (Kotlin, Scala, Clojure)

Java, introduced back in 1995, has been one of the most popular programming languages in the world of software development. To be honest, though, it’s had its fair share of criticisms over the years. From its verbose syntax to some quirks in performance and limited flexibility, developers have often found themselves wishing for something more modern. Enter alternatives like Scala (2004), Clojure (2007), and Kotlin (2016), which weren’t created solely to fix Java, but definitely addressed some of its pain points.

If you’ve worked with Java, you’ve probably had moments of frustration: “Why am I writing so much boilerplate code?”, “Do I really need to generate all these getters and setters?”, or “In a world full of beautiful, concise languages, why does this still feel so clunky?” These are questions that many developers have asked themselves while grappling with Java’s limitations.

Fast forward to today: Kotlin is almost a decade old, and Scala has just celebrated its 21st anniversary. In a constantly changing industry, it’s fair to wonder how Java has adapted over the years. Are its alternatives still as appealing as they once were? Or has Java managed to close the gap and prove it can stand the test of time? While the philosophies behind Scala, Clojure, and Kotlin go far beyond simply “fixing Java,” this article takes a comparative approach because that’s often how these languages are introduced in the conversation.

Language Comparison Overview

To understand where Java stands, let’s compare it with Kotlin, Scala, and Clojure across key dimensions:

• Java excels in enterprise applications and provides a more than mature ecosystem.
• Kotlin, a JetBrains-backed language, is still growing, particularly in Android development and backend services.
• Scala, known for its powerful functional programming features, is a favorite in the big data ecosystem (e.g., Apache Spark).
• Clojure, with its emphasis on immutability and concurrency, appeals to developers focused on modern functional programming but requires a Lisp mindset.

Productivity and Readability

One of the biggest critiques of Java has always been its verbosity, but newer JVM languages have faced this head-on:

Kotlin is celebrated for its concise syntax, built-in null safety, and incredible interoperability with Java. It significantly cuts down boilerplate code, making it an excellent choice for Android and modern backend development. Kotlin also integrates with Java-first frameworks like Spring, further improving its appeal.

That said, Java has made valuable efforts in closing the gap. While its null safety isn’t as clean as Kotlin’s, the introduction of Optional in Java 8 (2014) addressed some of these issues. Concurrent and asynchronous programming has also improved significantly, with CompletableFuture in Java 8 and, more recently, virtual threads in Java 21 (2024). Kotlin’s coroutines still offer great support in this area, but the gap between the two has narrowed.

Scala, on the other hand, offers unmatched flexibility by mixing functional and object-oriented paradigms. Its powerful type system and expressive syntax make it a go-to for data-heavy applications. However, its considerable learning curve and complexity can be a challenge for some developers.

Java has come a long way here too. When Scala debuted in 2004, Java lacked any meaningful support for functional programming. The introduction of lambda expressions and the Stream API in Java 8 drastically improved Java’s functional capabilities, and subsequent versions have continued to improve readability and performance.

Finally, Clojure prioritizes simplicity and immutability with its Lisp-inspired syntax. It’s highly effective for building concurrent systems, though its unique paradigm requires a significant learning investment.

As with Scala, Java has reduced the gap with Clojure’s features over time. The improved support for concurrency in Java 8, combined with functional programming features, has made Java a more viable option for scenarios where Clojure once had a clear advantage. Add to that the never-ending evolution of IDEs and, more recently, coding AIs, and many of these pain points are becoming less and less relevant.

Performance Considerations

When it comes to performance, Java remains the leader, largely due to its mature optimizations and fewer abstractions. While Kotlin and Scala introduce syntactic sugar that may slightly affect performance, these differences are negligible in most real-world scenarios. Clojure’s dynamic typing does make it slower compared to statically typed counterparts, but its flexibility often outweighs this trade-off in specific use cases.

Interoperability with Java

A key strength of JVM-based languages is their ability to interoperate with Java, allowing developers to leverage existing libraries and frameworks:

• Kotlin: Offers incredible interoperability, with minimal effort required to integrate Kotlin code into Java projects.
• Scala: While interoperable, differences in collections and its advanced type system can require additional care.
• Clojure: Although interoperable, its functional nature and Lisp-like syntax make Java integration less intuitive.

Use Cases and Industry Adoption

Each language has found its niche:

• Java: Continues to dominate enterprise applications, banking systems, and cloud solutions due to its stability and extensive support.
• Kotlin: Leads in Android development and is gaining fame in backend services, thanks to its modern syntax and interoperability.
• Scala: Preferred for big data and distributed systems, often used with frameworks like Apache Spark.
• Clojure: Finds its place in finance, AI/ML, and concurrent systems requiring immutability and lightweight concurrency.

Ecosystem and Community Support

Java enjoys the largest ecosystem, with frameworks like Spring, Jakarta EE, and advanced enterprise backing. Kotlin, backed by JetBrains, has a fast-growing community, particularly in Android and modern backend development. Scala, while powerful, has a more niche and specialized user base. Clojure’s community is small but passionate, appealing to functional programming enthusiasts.

With ongoing advancements such as Project Loom, Records, and Sealed Classes, Java continues to innovate, narrowing the gap with Kotlin and Scala in terms of expressiveness and concurrency support. Meanwhile, Kotlin’s adoption grows due to its developer-friendly features, and Scala remains relevant in data-intensive fields. Clojure, while niche, retains its appeal in concurrent programming and scripting.

Conclusion: Which One Should You Choose?

Choosing the right JVM language depends on your project’s requirements:

• Stick with Java for enterprise solutions, long-term support, and performance-critical applications.
• Opt for Kotlin if you prefer concise syntax, null safety, and a modern programming experience, especially for Android or backend development.
• Choose Scala for big data, distributed systems, or if you’re leveraging functional programming paradigms.
• Consider Clojure if immutability, simplicity, and concurrency are your priorities.

Many of the key advantages offered by Java's alternatives have been reduced over time, thanks to the revolutionary Java 8 release in 2014 and continuous improvements in subsequent versions, along with advancements in IDEs and the emergence of AI-powered coding tools.

While Java continues to be the foundation of the JVM ecosystem, these modern alternatives highlight the diverse options available to developers today. Depending on the use case and project goals, they provide specialized tools for building a wide range of applications.